In petroleum exploitation, submersible pump is one of the main apparatuses. Submersible pump, which is a multi-stage centrifugal pump, consists of multistage impellers, guide shell, pump shaft, pump housing, upper and lower joints and the like. As an important mechanical oil production apparatus, submersible pump has been widely used and developed in oilfield area at home and abroad.
The operating principle of the submersible pump is the same as that of the common ground centrifugal pump. Before starting submersible pump, pump body and suction line are filled with well fluid. After the unit in the oil well is started, submersible motor transfers mechanical energy to the submersible pump to rotate the pump shaft and the impellers on the pump shaft of the submersible pump at a high speed. The blades of the impellers drive the well fluid in the flow channel of the impellers to rotate. The liquid is thrown from the center of the impeller to the edge of the impeller due to the centrifugation force, accompanied by an increase of the kinetic energy. After the fluid enters the pump housing, since the flow channel is gradually expanded in the spiral-shaped pump housing, the flow speed of the liquid is gradually reduced, and a portion of the kinetic energy is converted into static energy, and thus the liquid flows out through the exit outlet at a higher pressure. At the same time, vacuum is formed in the center of the impeller because the liquid is thrown off. The pressure at the liquid level is higher than that at the center of the impeller. Therefore, the liquid in the suction line flows into the pump body under pressure difference. The well fluid flows through all impellers in the pump stage by stage and is pumped to ground oil collecting system.
During the operation of the submersible pump, the impellers are severely worn under the long term impact of the well fluid, and the possible solid impurity in the well fluid also aggravates such impact wear, which may change the main geometric dimensioning of the impellers and guide shell, reducing the service life of the submersible pump or even causing the submersible pump failure. Therefore, it is necessary to improve wear resistance of the impeller. However, if the impellers are manufactured by using material having higher hardness and wear resistance to solve the above problem, the manufacture process for the impellers becomes more difficult and complex, which is also not reasonable in terms of economy.
In the prior art, the surface of the impeller is usually modified, and a layer of wear resistant material is surfacing welded or spray welded (spray coated) onto the severely worn section of the impeller, so as to improve the wear resistance of the impeller. However, the existing wear resistant material has main components of Fe, Mo or Cr, which exhibits limited wear resistance and a hardness of 55˜65 HRC, and thus does not satisfy the production requirements.